I s s u e(s) :

On the meaning of the Space-Time concept as advanced by Albert Einstein in his Special Theory of Relativity as a physical foundation of studying Nature.

• The mathematical space structure of the Universe, according to Einstein's space-time concept, is a four (4) dimensional continuum composed of three (3) "regular" coordinates (x,y,z) plus a fourth one vested in the time coordinate (t), resulting in the space (x,y,z,t).
        - What is the mathematical, the physical, and the philosophical meaning of such a space?
  
• According to Einstein, the centuries old assumption that the space of the Universe is filled with a material substance (called ether or aether) should be abolished and substituted with vacuum.
        - In such a case, how could material perturbations, such as sound or light travel? Is it not required that a material perturbation to be able to propagate have a material medium of propagation?
        - Is there any physical principle prohibiting a limit to the speed of a material perturbation not to exceed the speed of light as postulated in Einstein's Special Theory of Relativity?
  

• In Einstein's Special Theory of Relativity, time is defined through clocks and the concept of simultaneity.
        - Can and should such a definition be acceptable? Don't we need to make a distinction between the theoretical concept of time and the practical way of measuring it?
        - What is the meaning of the simultaneity concept as advanced by Einstein in formulating the laws of Nature?